The Light Sources Themselves
The light sources themselves
Up to 8 point light sources may be defined, each of which is independently controllable. At the top level of the lighting panel they may be turned on/off and have their intensity set from 0 - 100%. The OpenGL standard requires all implementations to handle 8 light sources, although it is often the case that only one or two cab be handled in hardware: don't be surprised if setting up many lights causes a sudden and dramatic reduction in graphics speed!
To change any other attributes use the button. There are various preset options, and you can also specify your own light source positions or vectors.
Each may be "positional" (located at a specific point in space), or "directional" (infinitely distant along a vector). "Positional" light sources are more expensive for the hardware to calculate, and will slow down drawing, so only use them if you need to simulate the effects of a light close to your model.
Light sources can be fixed in screen space (stay fixed when the model moves), or attached to model space (move with the model). There is no significant difference in graphics speed between the two options.
All lights are white.
The "material" properties of the lit objects
and
| Brightness | Controls how light or dark the colour of the object is when illuminated, but the effect is to add matt colour (not whiteness, which would make it look shiny). |
| Shininess | Adds white highlights, but no colour, to make the object look shiny. |
These attributes (of the object, not the lights) are set in the PROPS box - see Properties: Controlling colour, drawing style, transparency, lighting attributes and overlay of entities .
1. OpenGL Programming Guide. Neider, Davis, Woo (ISBN 9 780201 632743)
2. Computer Graphics Principles and Practice. Foley, van Dam, Feiner, Hughes (ISBN 0 201 12110 7)